The number of routes which are stored in a router is increased along with increase of the number of communication devices which are included in a communication network. Therefore, an ID-Locator separation technique has attracted attention in recent years as a technique for avoiding increase in the amount of route information which is held by a router. Locator identifier separation protocol (LISP) is known as one of ID-Locator separation techniques.
FIG. 1 is a diagram illustrating an example of a network to which a LISP is applied. A network employing the LISP includes access networks A1, A2, a core network 3, and a location management server 10. The core network and the access networks are connected with each other by routers. Hereinafter, a router which belongs to both of a core network and an access network is referred to as an “edge node”, and a location address assigned to an edge node is abbreviated as a “LOC”. In the example of FIG. 1, the access network A1 and the core network 3 are connected with each other via an edge node 2a, and the access network A2 and the core network 3 are connected with each other via an edge node 2b. Further, in the example of FIG. 1, it is assumed that a router 4 is included in the access network A1 and a communication device 1a transmits a packet addressed to the core network 3 or the access network A2, to the edge node 2a via the router 4.
The location management server 10 acquires ID-LOC correspondence information from each edge node and holds the ID-LOC correspondence information in a position information management table 15. Here, ID-LOC correspondence information is a combination of an address (host ID) assigned to a communication device included in an access network in which an edge node is included and an address of the edge node. For example, the position information management table 15 depicted in FIG. 1 is generated when a host ID of the communication device 1a is IP1, a host ID of the communication device 1b is IP2, an address of the edge node 2a is LOC1, and an address of the edge node 2b is LOC2. Communication among communication devices belonging to different access networks is performed using ID-LOC correspondence information.
For example, a case where the communication device 1a transmits a packet 6 to the communication device 1b is described. The edge node 2a requests ID-LOC correspondence information including the host ID (IP2) of the communication device 1b which is a destination, from the location management server 10 (transmission of a LOC request message). The location management server 10 refers to the position information management table 15 so as to determine that an address associated with IP2 is LOC2. Further, the location management server 10 notifies the edge node 2a that an address assigned to the edge node of the access network to which IP2 belongs is LOC2, by using a LOC reply message. The edge node 2a stores the notified ID-LOC correspondence information in a LOC cache table 5. The edge node 2a generate an encapsulated packet 7 by encapsulating the packet 6 using a header (outer header) whose destination address is the address of the edge node notified from the location management server. The encapsulated packet 7 is routed to the edge node 2b by the outer header. The edge node 2b decapsulates the encapsulated packet 7 and transfers the packet 6 to the communication device 1b. Thereafter, upon receiving a packet addressed to the communication device 1b from the communication device 1a, the edge node 2a transfers the packet by using the information stored in the LOC cache table 5.
As the related art, such technique is known that when a mobile node transmits a packet to a node serving as a communication destination via a home agent, the mobile node transmits a packet 6 to the home agent by encapsulating the packet 6 addressed to the node serving as the communication destination. Here, there is a case where plural home addresses are assigned to a mobile node. In this case, the home agent is configured to detect a communication state of an internet service provider, and select an address to be set as a transmission source address of the packet 6 included in the encapsulated packet 7 based on the detected communication state.
International Publication Pamphlet No. WO 2006/104202 is an example of related art. Locator/ID Separation Protocol (LISP), draft-ietf-lisp-22.txt (Feb. 12, 2012) is an example of related art.